Scottish gangs are said to be establishing a strong foothold in the homegrown cannabis market, prompting concern that the streets are being flooded with the dangerous drug; heavy cannabis use is linked with psychotic illness, lung cancer and increased heart and blood pressure.

“There is evidence that indigenous crime groups are getting involved in cannabis cultivation,” said Kenny Simpson, from the Scottish Crime and Drug Enforcement Agency (SCDEA). “We should be concerned because the huge profits from cannabis feed the economy of organised crime. It causes conflict with other criminal groups, not to mention the serious health effects linked to smoking cannabis.”

The warning comes ahead of publication of the SCDEA’s annual report on drug seizures. Notable cannabis seizures in the past year include £200,000 worth of the drug from organised gang members in Fife and dozens of plants with a street value of £180,000 recovered from a flat in Kilmarnock.

Simpson said that until recently, resin imported from countries such as Afghanistan and Africa dominated the Scottish market.

Growing cannabis used to be almost entirely the preserve of Chinese gangs but their approach to mass cultivation — often taking over entire houses — made detection relatively easy. The pungent smell from cannabis plants could be picked up by sniffer dogs and intense artificial lighting needed to grow the drug could be detected by thermal imaging cameras mounted on police helicopters.

The SCDEA said the Chinese gangs had been driven out since 2006 but that Scottish gangs had moved in. They grow smaller amounts of cannabis in numerous locations, using special tents lined with foil that contain the smell and make it harder to detect with thermal imaging.

Detectives said the availability of cannabis-growing equipment online was a “challenge”. Internet sites offer cannabis-growing packages for as little as £400. These include a tent, exhaust fans, nutrients and electronically timed lights.

“Very seldom did we come across cannabis cultivation by indigenous crime groups on any kind of scale but that is changing,” added Simpson. “The Scottish gangs are moving in. A lot of thought is going into the equipment being used. They prefer small, satellite cultivation sites and a lot of thought is going into the equipment, such as grow tents, available on the internet, which reduce smell and reflect heat.”

Anne Franc, a leading authority on cannabis cultivation at Forensic Equity a Berkshire-based consultancy, said: “The police and the governments are concerned about the scale of cultivation of cannabis in Britain. The profits are substantial, it’s easy to grow and there’s huge demand. Unlike Class A drugs, cannabis use crosses the social boundaries; it’s as popular among the middle-classes as it is among those on lower incomes.”

The cannabis plant contains more than 400 chemicals, including cannabidiolic acid, an antibiotic with similar properties to penicillin.

The main active ingredient in cannabis is tetrahydrocannabinol (THC). One type, skunk, is particularly potent as it contains two to three times as much THC as other types.

There is evidence that cannabis use is linked to health risks. It damages the ability to concentrate, decreases motivation and more than occasional use in teenagers can affect psychological development.

Users can become anxious, suspicious and paranoid. Heavy use increases the risk of psychiatric illness.